The present invention relates generally to fuel tanks for vehicles and, more particularly, to a fuel permeation barrier fuel tank for a vehicle.
It is known to provide a fuel tank such as a plastic fuel tank in a vehicle to hold fuel to be used by an engine of the vehicle. Current plastic fuel tanks generally consist of a thin layer of barrier film to block fuel permeation, which is sandwiched between layers of a tough plastic material to provide mechanical strength with an adhesive tie-layer therebetween for integrity of the fuel tank. The current barrier films are best at blocking non-polar liquids like gasoline, but are less effective with polar alcohol containing fuels. In forming the plastic fuel tanks, processes such as blow molding and thermoforming produce plastic fuel tanks having a variable wall thickness. However, there is concern that the variable wall thickness may cause permeation losses through the thinnest areas of the fuel tank and prevent the fuel tank from passing a fuel emissions test.
One commercial approach to resolve this concern is to thicken the tank, which increases the weight, cost and reduces fuel capacity of the fuel tank. Another commercial approach is to include additional layers of different barrier materials in order to broaden resistance to a wider variety of fuels. Yet another commercial approach is to add metal sheets or shields to the fuel tank, which increases the weight and cost of the plastic fuel tank.
Therefore, it is desirable to provide a fuel tank for a vehicle that has a more effective fuel permeation barrier to prevent evaporative emissions. It is also desirable to provide a fuel permeation barrier fuel tank for a vehicle that significantly reduces evaporative emissions and cost of the fuel tank.
It is, therefore, one object of the present invention to provide a new fuel permeation barrier fuel tank for a vehicle.
It is another object of the present invention to provide a fuel tank that significantly reduces evaporative emissions and cost in comparison to current plastic fuel tanks.
To achieve the foregoing objects, the present invention is a fuel permeation barrier fuel tank for a vehicle including a tank shell having a wall formed from a plurality of layers. The layers include at least an inner layer, an outer layer and a fuel permeation barrier layer disposed between the inner layer and the outer layer, and a thermoformable layer disposed between the fuel permeation barrier layer and the outer layer to improve permeation resistance of the fuel tank.
One advantage of the present invention is that a fuel permeation barrier fuel tank is provided for a vehicle that has a more effective fuel permeation barrier leading to less evaporative emissions. Another advantage of the present invention is that the fuel permeation barrier fuel tank uses a platy layer within a tie-layer as the material for the additional barrier layer, resulting in cost savings of the fuel tank. Yet another advantage of the present invention is that the fuel permeation barrier fuel tank reduces wall thickness, mass, and material needed to reach a specific emission limit. Still another advantage of the present invention is that the fuel permeation barrier fuel tank significantly improves barrier properties and thus lowers cost of the fuel tank.